The invention relates to sewing machines and more particularly to a presser foot lifting mechanism for a sewing machine.
One conventional way of lifting a presser foot in an industrial lock-stitch type sewing machine is illustrated in FIG. 6 with its sectional view. Referring to FIG. 6, a presser foot 53 is urged to press a throat plate 52 by a presser spring 51. A solenoid 54 is excited by a knee-operated switch 56 which is recessed in a knee abutment member 55. The presser foot is lifted by the solenoid action via a lever 57, a presser rod 59 which is located in a oil pan 58, a bar 60, a lever 61, a connecting rod 62, a lever 63 and finally by a stop rod 65. Thus the presser foot is lifted from the throat plate.
In such conventional means, presser foot lifting fatigue experienced by an operator may be lessened by the force of the solenoid 54. However, the position of the presser foot is defined only by two points, the lowest point touching with the throat plate and the highest point responding to the maximum stroke of the solenoid. Thereby, when the workpiece is thick or when the presser foot is to be positioned at an intermediate point to place the workpiece or to ease the operation, the mechanism was inconvenient and led to operator fatique. The embodiment of the foregoing "presser foot lifting mechanism" invention is disclosed in PCT application No. JP-84/00140.
It is therefore an object of the invention to provide a presser foot lifting mechanism for a sewing machine which is effective to lessen operator fatigue.